The invention relates to a hybrid vehicle battery temperature control method and apparatus.
Hybrid electric vehicles comprise an internal combustion engine and an electric machine. The electric machine is supplied with traction power at least partly from a battery.
It is known that temperature has an influence over battery performance. As the battery is being charged, the temperature of the battery may increase due to a chemical reaction of the battery solution. The temperature increase during charging may accelerate corrosion and degradation of the positive electrode. Therefore, a too high temperature of the battery may lower its performance and shorten its lifetime. Similarly, a too low temperature of the battery may also decrease its performance and lifetime. A desired operating temperature for a lead acid battery is 25° C.-40° C. while a lithium ion battery may have a desired operating temperature range of 0° C.-40° C.
In view of the above it is desired to control the temperature of the battery in a hybrid vehicle in order to extend the lifetime of the battery.
In U.S. Pat. No. 7,147,071 it is disclosed a hybrid electrical vehicle with a battery temperature regulating device. The device comprises an internal combustion engine coolant circuit and a battery coolant circuit. Heat is transferred between the circuits via a heat exchanger.
A problem with the solution proposed in U.S. Pat. No. 7,147,071 is the high cost for the heat exchanger and that the coolant circuit for the engine must be redesigned.
It is desirable to provide a method for controlling the temperature of a traction battery in a hybrid vehicle which overcomes the above mentioned problems.
In a first example embodiment according to an aspect of the invention it is provided a method for controlling the temperature of a traction battery in a hybrid vehicle, where said hybrid vehicle comprises an internal combustion engine and an electric motor for traction power, comprising the steps of: providing a first temperature regulating circuit for the internal combustion engine, providing a second temperature regulating circuit for the traction battery, heating the traction battery by an electrical heater provided in said second temperature regulating circuit in series with a pump, a radiator and said traction battery, transferring power to said electrical heater via a DC/DC converter from the electrical motor, which electrical motor is driven by said internal combustion engine, while said battery is below a predetermined temperature interval.
An advantage with this example embodiment is that the power for heating the battery is provided from the internal combustion engine via a DC/DC converter and said electrical motor.
In another example embodiment according to the present invention said method further comprising the step of using said battery for traction power only when said battery has a temperature within said predetermined temperature interval.
An advantage with this example embodiment is that the lifetime of the battery may be extended.
In another example embodiment according to the present invention said method further comprising the steps of providing a bypass circuit for said radiator in said second temperature regulating circuit, regulating a flow of liquid coolant into the radiator or into the bypass circuit by a valve.
An advantage with this example embodiment is that the time for reaching a working temperature of the battery may be decreased.
In another example embodiment of the present invention said method further
comprising the step of: controlling said electric motor by a voltage target value for feeding power to the heater when said battery is below said predetermined temperature interval.
An advantage with this embodiment is that the electrical components life time may be increased and its performance may be secured.
In another example embodiment according to the present invention said method further comprising the step of: isolating said second temperature regulating circuit from said first temperature regulating circuit.
An advantage of this example embodiment is that the first and second temperature regulating circuits can be controlled independently of each other.
The invention also relates to a system for controlling the temperature of a traction battery in a hybrid vehicle, where said hybrid vehicle comprises an internal combustion engine and an electric motor for traction power, said system
comprising: a first temperature regulating circuit for the internal combustion engine, a second temperature regulating circuit for the traction battery, a heater, a pump and a radiator provided in said second temperature regulating circuit, said heater is provided with power via a DC/DC converter from the electrical motor, which electrical motor is driven by said internal combustion engine.
An advantage with this example embodiment is that the power for heating the battery is provided from the internal combustion engine via a DC/DC converter and said electrical motor.
In another example embodiment of the present invention said system further comprising a bypass circuit for said radiator in said second temperature regulating circuit, a valve for regulating a flow of liquid coolant into the radiator or into the bypass circuit.
An advantage with this example embodiment is that the time for reaching a working temperature of the battery may be decreased.
In yet another example embodiment according to the present invention said system further comprising a controller for controlling said electric motor by a voltage target value for feeding power to the heater when said battery is below said predetermined temperature interval.
An advantage with this embodiment is that the electrical components life time may be increased and its performance may be secured.
In still another example embodiment of the present invention said first and second temperature regulating circuits are isolated from each other.
An advantage of this example embodiment is that the first end second temperature regulating circuits can be controlled independently of each other.
In the drawings, equal or similar elements are referred to by equal reference numerals. The drawings are merely schematic representations, not intended to portray specific parameters of the invention. Moreover, the drawings are intended to depict only typical embodiments of the invention and therefore should not be considered as limiting the scope of the invention.